Make sure the 19mm bolt in the tensioner itself is loosened before you try to adjust the tensioner bolt. Not doing this could either strip the adjuster threads or see below. The adjuster is reverse thread. If there is no adjustment happening then the tensioner will be toast - a M103 weak point. Don't start messing with the alternator - you can damage the bearing in it. Change the tensioner. - It's a PITA to change but straight forward.